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xen-netback: avoid race that can lead to NULL pointer dereference

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In function xenvif_disconnect_queue(), the value of queue->rx_irq is
zeroed *before* queue->task is stopped. Unfortunately that task may call
notify_remote_via_irq(queue->rx_irq) and calling that function with a
zero value results in a NULL pointer dereference in evtchn_from_irq().

This patch simply re-orders things, stopping all tasks before zero-ing the
irq values, thereby avoiding the possibility of the race.

Fixes: 2ac061ce97 ("xen/netback: cleanup init and deinit code")
Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Acked-by: Wei Liu <wei.liu@kernel.org>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
This commit is contained in:
Paul Durrant 2019-12-13 13:20:40 +00:00 committed by Jakub Kicinski
parent 858ce8ca62
commit fd42bfd1bb
1 changed files with 12 additions and 12 deletions
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24
drivers/net/xen-netback/interface.c
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@ -628,18 +628,6 @@ int xenvif_connect_ctrl(struct xenvif *vif, grant_ref_t ring_ref,
static void xenvif_disconnect_queue(struct xenvif_queue *queue)
{
if (queue->tx_irq) {
unbind_from_irqhandler(queue->tx_irq, queue);
if (queue->tx_irq == queue->rx_irq)
queue->rx_irq = 0;
queue->tx_irq = 0;
}
if (queue->rx_irq) {
unbind_from_irqhandler(queue->rx_irq, queue);
queue->rx_irq = 0;
}
if (queue->task) {
kthread_stop(queue->task);
queue->task = NULL;
@ -655,6 +643,18 @@ static void xenvif_disconnect_queue(struct xenvif_queue *queue)
queue->napi.poll = NULL;
}
if (queue->tx_irq) {
unbind_from_irqhandler(queue->tx_irq, queue);
if (queue->tx_irq == queue->rx_irq)
queue->rx_irq = 0;
queue->tx_irq = 0;
}
if (queue->rx_irq) {
unbind_from_irqhandler(queue->rx_irq, queue);
queue->rx_irq = 0;
}
xenvif_unmap_frontend_data_rings(queue);
}